Brand New G4KJ 2.4L GDI Petrol Long Engine for Hyundai i45 / Sonata YF

About this engine

A seized or knocking engine doesn’t have to be the end of a good sedan. Engine Zone offers a brand-new G4KJ 2.4L GDI petrol long engine for the Hyundai i45 — badged Sonata YF in overseas markets — giving owners a factory-fresh replacement instead of a gamble on used parts.

The engine is built new throughout to OEM fitment specification — and where the original design carried documented weaknesses, the internals are upgraded rather than copied. Nothing about it is recycled: block, head and every internal component are new, and each completed engine must pass a hot and cold test before we will crate it. Buyers get free freight to any Australian address, a 12-month/50,000 km parts warranty, and a no-cost VIN check so fitment is confirmed in advance. Everything else you need to know — the engine’s family history, inclusions, and the installation path — is laid out below, or phone 1300 200 320.

Is it worth putting a new engine in an i45?

Run the numbers before you decide. An i45 with a dead engine has scrap-adjacent value, yet the same car with a documented new engine drives, sells and insures like the tidy mid-size sedan it was last week. The gap between those two positions is the fitted cost of a replacement engine — and that gap is usually smaller than the changeover cost to a comparable used car, which arrives with its own unknowns.

The condition of the rest of the vehicle should steer the call. Check the transmission's behaviour, the service history, rust, tyres and suspension. If the car scores well everywhere except under the bonnet, replacement is rational. If the engine failure is just the loudest of several problems, put the money toward the next car instead.

Also think about horizon. An owner keeping the car two more years might squeak by with a used engine and some luck. An owner planning five or more years of service wants the option with new internals and a warranty behind it, because a second engine failure would sink the economics completely. That long-horizon logic is exactly who a brand-new G4KJ long engine is for. Get a fitting quote from your workshop, add our engine price, and compare the total against changeover cost on a replacement vehicle — the comparison usually takes five minutes and settles the argument.

The Theta II's common problems — and how this engine answers them

The G4KJ in the i45 is one branch of the Theta II tree, the four-cylinder petrol architecture Hyundai and Kia deployed across sedans and SUVs through the 2010s. Its relatives are the G4KE (2.4, multi-point injection), the G4KH (a turbocharged 2.0-litre with direct injection) and the G4KG. Common to all of them: an aluminium four-cylinder layout, twin cams, 16 valves, and camshaft drive by chain, meaning owners never face a timing belt bill.

Within the family, the G4KJ stands out for its gasoline direct injection. Fuel is delivered at high pressure straight into each combustion chamber, which sharpens throttle response and trims consumption relative to the port-injected G4KE. Direct injection across the entire industry brings one maintenance consideration with it: intake valves no longer get rinsed by fuel, so carbon can settle on them gradually. It is a servicing topic, not a defect in the engine you are buying, and it develops over years rather than months.

The family's documented weak point sits lower in the engine. Rod-bearing wear in high-kilometre Theta II engines is well recorded, to the point that several markets ran recall and extended-warranty campaigns. The plain-English consequence for an i45 owner: when the bottom end goes, the whole engine is generally uneconomic to save, and a complete replacement is the fix the trade has settled on. Buying that replacement new — rather than second-hand with the same design and unknown wear — is how you avoid revisiting the problem. This engine goes further than simply being new: while fitment follows the OEM specification exactly, the connecting rods, crankshaft and bearings inside are made to a higher grade than the factory originals, reinforcing the design at its documented weak point instead of reproducing it.

What arrives, what transfers, and who fits it

The product is a long engine, which in trade terms means the complete assembled rotating and reciprocating package: block, crankshaft, pistons and rods, plus the cylinder head with camshafts and valvetrain fitted and timed. Think of it as everything sealed inside the engine, ready for the outside world to be bolted on.

That outside world comes from your existing engine. Intake and exhaust manifolds, injectors and the high-pressure pump, sensors, the starter and alternator, air-conditioning compressor and mounting hardware are all standard transfer items. Your mechanic handles this as part of the installation, and it is worth having them assess each transferred part — a perished hose or tired water pump has no place on a new engine.

Three checkpoints protect you through the process. Before purchase, the free VIN verification confirms the engine suits your i45 exactly. Before dispatch, hot and cold testing proves the engine runs correctly. After installation, the heat tab on the block stands guard: it permanently records any overheating event, and an overheated engine is outside warranty, so cooling system care is essential from the first drive.

The parts warranty spans 12 months or 50,000 km, whichever lands first. Freight is included Australia-wide. Fitting must be done by a qualified mechanic — both for the warranty and because a correct first start, priming and coolant bleed set the engine up for its whole service life. Ring 1300 200 320 with anything unresolved.